1. Field of the Invention
This invention relates to a data recording and reproducing device for recording and reproducing analog signals such as music signals and image signals in a digital mode.
2. Description of the Prior Art
In a digital audio device for recording and reproducing music signals in a digital mode, a music signal is sampled with a predetermined sampling frequency so that it is converted into a digital signal of several bits per sampling, for instance sixteen (16) bits per sampling, and the digital signal thus obtained is recorded. If, in this case, the "fortissimo" of a music signal (loud portions) is recorded with full bits (all the bits being "1"), then a small signal such as "pianissimo" (soft portions) will be recorded with only a few bits; that is, the recording operation is greatly affected by quantization noise.
In order to minimize the effect of quantization noise, several methods have been provided for the signal reproducing device. For instance, in one method, a digital filter is used to multiply the sampling frequency, and the data value obtained is outputted with up to eighteen bits, so that it is converted into an analog signal with an 18-bit DA converter. Another method, applies to the case where a digital signal recorded on a recording medium is converted into an analog signal with a DA (digital-to-analog) converter, and a small signal is utilized in which the effective bits are not high-order bits. The digital signal is subjected to digital-to-analog conversion after being shifted to the high-order bits, and the gain obtained through the shifting of the signal is attenuated by the analog circuit on the output side to thereby obtain the original signal level.
In each of these methods, during recording of data on the recording medium, the data as well as quantization noise is recorded. Accordingly, improvement of the signal reproducing device by these conventional methods is limited. That is, since only fixed data of 16 bits per sampling is recorded on the recording medium, the data may be improved to the accuracy of 16 bits. Based on theis limitation, it is fundamentally impossible to obtain data having a higher accuracy. Accordingly, in the conventional methods, the small signal cannot be improved with respect to the quantization noise.